Every atom contributes one free electron in copper. If $1.1 \ A$ current is flowing in a copper wire having a $1 \ mm$ diameter,then the drift velocity (approx.) will be (Density of copper $= 9 \times 10^3 \ kg \ m^{-3}$ and atomic weight $= 63$).

$A$ wire has a non-uniform cross-section as shown in the figure. $A$ steady current flows through it. The drift speed of electrons at points $P$ and $Q$ is $v_P$ and $v_Q$ respectively.

$A$ $1\,m$ long copper wire carries a current of $1\,A$. If the cross-section of the wire is $2.0\,mm^{2}$ and the resistivity of copper is $1.7 \times 10^{-8}\,\Omega\,m$,the force experienced by a moving electron in the wire is $x \times 10^{-23}\,N$. Find the value of $x$. (Charge on electron $= 1.6 \times 10^{-19}\,C$)

Derive the equation of mobility in terms of electric current.

$A$ current of $1.6\, A$ is flowing through a wire having a cross-sectional area of $1\, mm^2$. If the density of free electrons in the material of the wire is $10^{29}\, m^{-3}$,the drift velocity of the electrons will be:

Assertion : The electric bulb glows immediately when the switch is on.
Reason : The drift velocity of electrons in a metallic wire is very high.